1. Field of the Invention
The present invention relates to an absorbent article suitable for absorbing menstrual blood and so on discharged from the female genital organ, more particularly, relates to an absorbent article having resilient portions for restoring the article to its original state even when it is deformed by compression or twisted during wear, and a method for manufacturing the same.
2. Related Art
Absorbent articles intended to absorb menstrual blood discharged from a female genital organ are typically constructed to include an absorbent layer, a liquid-permeable topsheet covering the skin surface of the absorbent layer, and a liquid-impermeable backsheet covering the garment surface of the absorbent layer. Generally, they are worn with the backsheet adhered to an inner side of a groin piece of an undergarment through a pressure-sensitive adhesive layer.
In order to certainly collect liquid discharged from an excretory part of a wearer by the absorbent article, the skin surface is preferably brought into close contact with the wearer's excretory part. If a clearance is caused between the skin surface of the absorbent article and the excretory part when the absorbent article is worn in the crotch, discharged liquid applied to the topsheet may flow along the topsheet to easily cause leakage laterally of the absorbent article or leakage toward the wearer's buttocks, which results in fouling the undergarment or other garments.
As disclosed in the following Patent Publications 1 to 3, therefore, there have been developed absorbent articles in which a portion between grooves formed in the skin surface is raised for close contact with the wearer's excretory part.
Patent Publication 1 discloses an absorbent article, in which a raised portion where an absorbent body is of an increased thickness is provided centrally while a pair of curved top-side grooves is formed on right and left sides of the raised portion. The top-side grooves can serve as a flexible hinge to facilitate folding of the absorbent body, which aims at deforming the raised portion to have an arc cross-section projecting toward the wearer.
Patent Publication 2 discloses an absorbent article, in which a skin contact surface has a longitudinally elongated projection surrounded by a recess. This aims at raising the projection for closely contacting the wearer's excretory part as well as at blocking liquid by the recess surrounding the projection for preventing diffusion to surroundings.
Patent Publication 3 discloses a substantially longitudinally elongated absorbent article, in which arc-shaped folding portions inwardly curved from longitudinal side edges are provided on a region where an absorbent body is present, so that leakage preventing wall forming regions are formed in the portions confined in the folding portions. The leakage preventing wall forming regions intended to rise toward the wearer's crotch at the time of wearing aim at preventing lateral leakage of discharged liquid.
[Patent Publication 1]
Japanese Unexamined Patent Publication No. 10-328232
[Patent Publication 2]
Japanese Unexamined Patent Publication No. 11-33054
[Patent Publication 3]
Japanese Unexamined Patent Publication No. 8-322875
FIG. 15 is a sectional view schematically showing a state where such an absorbent article as disclosed in Patent Publications 1 to 3 is worn.
Referring to FIG. 15, the wearer's crotch and thighs are indicated by 50 and 51, a groin piece of an undergarment to be applied to the crotch 50 is indicated by 25, and the conventional absorbent article is indicated by 60. This absorbent article 60 is adhered to and fixed on an inner side of the groin piece 25. In the foregoing Patent Publications, a pair of grooves 61, 61 is formed in the skin surface of the absorbent article 60 so that a central portion 62 between the grooves 61, 61 can closely contact an excretory part in the crotch 50.
When the absorbent article 60 is worn as attached to the groin piece 25, as shown in FIG. 15, a lateral compressive force F is frequently applied to the groin piece 25 and the absorbent article 60 from the thighs 51, 51 during walking. The compressive force makes the right and left grooves 61, 61 approach each other, so that the lateral compressive force acts on the central portion 62 between the grooves 61, 61.
In the conventional absorbent article 60, however, resiliency against the lateral compressive force mainly depends on resiliency of absorbent layer provided in the central portion 62. Because the absorbent layer in the central portion 62 need feel soft to the crotch 50 and its liquid absorption capacity need be increased, its basis weight is high, whereas its density is low. Accordingly, when compressed and deformed, as shown in FIG. 15, its lateral resiliency is so poor that its width cannot be easily restored from the compressed and deformed state. When the absorbent article is twisted as a whole in accordance with the motion of the crotch, on the other hand, it cannot be easily restored from the twisted state.
Particularly when the absorbent layer is of a high basis weight and a low density, as set forth above, its resiliency decreases after absorption of discharged liquid such as menstrual blood, so that its bulkiness cannot be restored once the central portion 62 is crushed by pressure from the crotch 50 and its lateral resiliency against compression due to the compressive force F decreases drastically. Therefore, even after the thighs 51, 51 are spread wide, the absorbent article remains compressed laterally or twisted, decreasing the area of the skin surface of the absorbent article 60 and easily forming a space between the article and the crotch 50, which easily results in causing lateral leakage.
Furthermore, since the conventional ones disclosed in the foregoing Patent Publications are all constructed such that the grooves 61 are disposed one on each side, side portions 63, 63 outside the grooves 61 easily contact the central portion 62 when deformed as shown in FIG. 15. As a result, discharged liquid applied to the central portion 62 tends to migrate to the side portions 63, 63 and diffuse laterally of the absorbent article 60. That is, the effect of diffusing discharged liquid through the grooves 61, 61 cannot be achieved, which easily results in causing lateral leakage of discharged liquid.
In order to prevent lateral leakage of discharged liquid applied to the absorbent article, there have been developed leakage preventing walls extending longitudinally and opposed laterally on the skin surface of the absorbent article. The leakage preventing walls are constructed with elastic members for producing a longitudinal elastic shrinkage force disposed on a liquid-impermeable sheet, so that the sheets rise from the skin surface due to the elastic shrinkage force.
However, the conventional absorbent article is easily deformed or twisted during wear because its shape retention may be deteriorated when the absorbent article is subjected to the compressive force F or absorbs discharged liquid. In this case, front and rear rising points of the leakage preventing walls easily move toward the longitudinal centerline due to deformation of the article or move longitudinally due to twisting of the absorbent article. Accordingly, since the standing position of the leakage preventing walls is unstable, the leakage preventing walls may possibly twist or fall down toward the longitudinal centerline, decreasing the liquid absorption area of the skin surface.
In case where the leakage preventing walls are disposed in such a long absorbent article as disclosed in Patent Publications 1 and 2, the leakage preventing walls become more unstable since the length of the leakage preventing walls need be increased. When a long absorbent article of this type is worn, the leakage preventing walls may move unexpectedly following the motion of the wearer's body, which results in causing twisting or falling down of the leakage preventing walls more easily.